JP7251548B2 - Heavy duty pneumatic tire and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heavy duty pneumatic tire and a manufacturing method thereof.

A tread of a heavy-duty pneumatic tire is usually cut with circumferential grooves extending continuously in the circumferential direction. As a result, a plurality of axially parallel land portions are formed on the tread. A land area located at the equator is referred to as a center land area. A land portion located at the end portion of the tread surface is called a shoulder land portion.

The circumferential length difference from the equator gradually increases from the equator toward the outside in the axial direction. Since the shoulder land portion easily slides on the road surface, the shoulder land portion is likely to be worn.

Abrasion of the shoulder land portion, that is, uneven wear of the tire causes a change in the tire's ground contact pressure distribution as well as the appearance of the tire, and thus may deteriorate the running performance and durability. Various studies have been made to suppress the occurrence of uneven wear (for example, Patent Document 1).

JP 2008-049967 A

In order to suppress the occurrence of uneven wear, various investigations centering on the optimization of the tread profile have been conducted. However, the actual situation is that a technology capable of completely suppressing the occurrence of uneven wear has not yet been established.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heavy-duty pneumatic tire in which the occurrence of uneven wear is suppressed.

The present inventors have made intensive studies on techniques for suppressing the occurrence of uneven wear, and have found that it is possible to control the radial runout at the equatorial portion of the tread, that is, the center portion, as well as the radial runout at the edge portion of the tread, that is, the shoulder portion. This makes it possible to suppress the occurrence of uneven wear, and by stipulating not only the stretch of the center part of the belt when pressurizing and heating the raw tire in the mold, but also the stretch of the edge part of the belt, the radial runout is effective. The present invention has been completed by finding that it can be controlled effectively.

A heavy-duty pneumatic tire according to one aspect of the present invention is a heavy-duty pneumatic tire obtained by vulcanization molding of a raw tire, comprising a tread that contacts a road surface and a belt positioned radially inward of the tread. Prepare. The tread comprises a tread surface having a radially outwardly convex profile, the tread surface comprising a crown portion that includes the equator of the tire, and a pair of side portions that are axially outward of the crown portion. wherein the profile of the crown portion is represented by an arc having radius Rc, and the profile of the side portion is represented by an arc having radius Rs. By forming at least three circumferential grooves in the tread, at least four land portions arranged in parallel in the axial direction are formed. , and the land portion located on the outer side in the axial direction is the shoulder land portion. The belt is composed of a plurality of layers laminated in the radial direction, and each layer includes a number of belt cords inclined with respect to the circumferential direction. Among the plurality of layers, the layer having the widest axial width is the first reference layer, and the layer laminated outside the first reference layer is the second reference layer, which is positioned on the innermost side in the radial direction. The third reference layer is the layer where The ratio of the center stretch Sc represented by the following formula (2) at the center of the third reference layer to the shoulder stretch Ss represented by the following formula (1) at the end of the third reference layer is 1 3 or less, and the shoulder stretch Ss is 1% or more.
(shoulder stretch) 100×(Rsa-Rsb)/Rsb (1)
(Center stretch) 100×(Rca-Rcb)/Rcb (2)
(where Rsa is the inner diameter of the edge of the third reference layer in the tire, Rsb is the inner diameter of the edge of the third reference layer of the green tire, and Rca is the inner diameter of the center of the third reference layer of the tire. and Rcb is the inner diameter of the center of the third reference layer in the raw tire.)

Preferably, in this heavy-duty pneumatic tire, the at least three circumferential grooves include a center circumferential groove located on the inner side in the axial direction and a shoulder circumferential groove located on the outer side. The shoulder circumferential groove is narrower than the center circumferential groove.

Preferably, in this heavy-duty pneumatic tire, the shoulder stretch Ss is 2% or less.

Preferably, in this heavy-duty pneumatic tire, the overall value of the radial runout at the center portion of the tread is 1.5 mm or less, and the overall value of the radial runout at the shoulder portion of the tread is 1.5 mm or less.

Preferably, in this heavy-duty pneumatic tire, the absolute value of the difference between the overall value of the radial runout at the center portion and the overall value of the radial runout at the shoulder portion is 0.5 mm or less.

Preferably, in this heavy-duty pneumatic tire, the absolute value of the difference between the radial runout at the center portion and the radial runout at the shoulder portion at each circumferential portion of the tread is 0.20 mm or less.

Preferably, in this heavy-duty pneumatic tire, the shoulder land portion extends continuously in the circumferential direction without interruption.

Preferably, the heavy-duty pneumatic tire includes a narrow land portion located outside the shoulder land portion in the axial direction and extending in the circumferential direction. A narrow vertical groove is provided between the narrow land portion and the shoulder land portion, and the narrow vertical groove is located outside the end of the first reference layer in the axial direction.

Preferably, in this heavy duty pneumatic tire, the axial width of the first reference layer is equal to or narrower than the axial width of the tread surface.

Preferably, in this heavy duty pneumatic tire, the actual width of the shoulder land portion is wider than the actual width of the center land portion.

Preferably, in this heavy-duty pneumatic tire, in at least one layer among the plurality of layers forming the belt, the belt cord has an inclination angle at the end of the layer equal to the inclination angle at the equatorial plane.

Preferably, in this heavy-duty pneumatic tire, the inclination angle of the belt cords on the equatorial plane is 12° or more and 20° or less in the first reference layer and the second reference layer.

Preferably, in this heavy-duty pneumatic tire, the tire thickness measured along the normal to the inner surface of the tire passing through the edge of the tread surface is greater than the tire thickness measured along the equatorial plane. thick.

Preferably, in this heavy duty pneumatic tire, the radius Rs of the arc representing the profile of the side portion is larger than the radius Rc of the arc representing the profile of the crown portion.

A method for manufacturing a heavy duty pneumatic tire according to one aspect of the present invention provides a heavy duty pneumatic tire comprising a tread that contacts a road surface and a belt positioned radially inward of the tread. A method for manufacturing using a vulcanization apparatus comprising
(1) preparing a green tire including the tread and the belt;
(2) a step of putting the green tire into a mold; and (3) a step of expanding the diameter of the green tire in the mold and pressurizing and heating the tire. The belt is composed of a plurality of layers laminated in a radial direction, and among the plurality of layers, the layer having the widest axial width is a first reference layer, and is laminated on the outer side of the first reference layer. The layer is the second reference layer, and the radially innermost layer is the third reference layer. The ratio of the center stretch Sc represented by the following formula (2) at the center of the third reference layer to the shoulder stretch Ss represented by the following formula (1) at the end of the third reference layer is 1 3 or less, and the shoulder stretch Ss is 1% or more.
(Shoulder stretch Ss) 100×(Rsa−Rsb)/Rsb (1)
(Center stretch Sc) 100×(Rca−Rcb)/Rcb (2)
(where Rsa is the inner diameter of the edge of the third reference layer in the tire, Rsb is the inner diameter of the edge of the third reference layer of the green tire, and Rca is the inner diameter of the center of the third reference layer of the tire. and Rcb is the inner diameter of the center of the third reference layer in the raw tire.)

In the heavy duty pneumatic tire of the present invention, the stretch of the belt specified based on the inner diameter of the belt in the raw tire and the inner diameter of the belt in the tire obtained by pressurizing and heating the raw tire is within a predetermined range. set. As a result, in this tire, the radial runout at the center portion of the tread and the radial runout at the shoulder portions of the tread are well balanced. The tread of this tire is less likely to have a portion (for example, unevenness) that may become a starting point of uneven wear. In this tire, the occurrence of uneven wear is suppressed.

FIG. 1 is a cross-sectional view showing a portion of a heavy-duty pneumatic tire according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the arrangement of belt cords included in the belt. 3 is a developed view showing the tread surface of the tire of FIG. 1. FIG. FIG. 4 is an explanatory diagram illustrating the profile of the tread surface of the tire. FIG. 5 is a diagram for explaining stretching of the belt during vulcanization molding. 6 is an enlarged cross-sectional view showing a portion of the tire of FIG. 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

In the present invention, a state in which the tire is mounted on a rim (normal rim), the internal pressure of the tire is adjusted to the normal internal pressure, and no load is applied to the tire is referred to as a normal state. In the present invention, the dimensions and angles of the tire and each portion of the tire are measured under normal conditions unless otherwise specified.

Regular rim means a rim defined in the standard on which the tire relies. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims.

The normal internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in JATMA standards, the "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standards, and the "INFLATION PRESSURE" in ETRTO standards are regular internal pressures.

Normal load means the load specified in the standard on which the tire relies. The "maximum load capacity" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

FIG. 1 shows part of a heavy-duty pneumatic tire 2 (hereinafter sometimes simply referred to as "tire 2") according to one embodiment of the present invention. This tire 2 is mounted, for example, on heavy-duty vehicles such as trucks and buses.

FIG. 1 shows part of a cross-section of this tire 2 along a plane containing the axis of rotation of the tire 2 . In FIG. 1 , the horizontal direction is the axial direction of the tire 2 and the vertical direction is the radial direction of the tire 2 . The direction perpendicular to the paper surface of FIG. 1 is the circumferential direction of the tire 2 . In this FIG. 1 , the dashed-dotted line CL represents the equatorial plane of the tire 2 .

In FIG. 1, the tire 2 is mounted on the rim R. This rim R is a regular rim. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted to a normal internal pressure. No load is applied to this tire 2 .

The tire 2 comprises a tread 4, a pair of sidewalls 6, a pair of beads 8, a pair of chafers 10, a carcass 12, a belt 14, a cushion layer 16, an inner liner 18, a pair of steel reinforcement layers 20 and a pair of fiber reinforcements. A layer 21 is provided.

The tread 4 is made of crosslinked rubber. The tread 4 contacts the road surface on its outer surface 22 . The outer surface 22 of the tread 4 is the tread surface. This tread 4 comprises a tread surface 22 . Reference character PC in FIG. 1 indicates an intersection point between the tread plane 22 and the equatorial plane. This intersection point PC is the equator of this tire 2 .

In this tire 2 , at least three circumferential grooves 24 are cut in the tread 4 . Thereby, at least four land portions 26 are formed on the tread 4 .

Each sidewall 6 continues to the edge of the tread 4 . Sidewalls 6 extend radially inward from the ends of tread 4 . An outer surface 28 of the sidewall 6 forms the side surface of the tire 2 . The sidewall 6 is made of crosslinked rubber.

Each bead 8 is located radially inside the sidewall 6 . Bead 8 comprises core 30 and apex 32 .

Core 30 extends in the circumferential direction. Core 30 includes a wound steel wire 34 . Core 30 has a substantially hexagonal cross-sectional shape. The apex 32 is located radially outside the core 30 . Apex 32 extends radially outward from core 30 . The apex 32 includes an inner apex 32u and an outer apex 32s. The inner apex 32u and the outer apex 32s are made of crosslinked rubber. The outer apex 32s is softer than the inner apex 32u.

Each chafer 10 is positioned axially outside the bead 8 . The chafer 10 is located radially inside the sidewall 6 . The chafer 10 contacts the seat S and the flange F of the rim R. The chafer 10 is made of crosslinked rubber.

A carcass 12 is located inside the tread 4 , sidewalls 6 and chafer 10 . Carcass 12 comprises at least one carcass ply 36 . The carcass 12 of this tire 2 consists of one carcass ply 36 .

Although not shown, the carcass ply 36 includes a number of parallel carcass cords. These carcass cords are covered with a topping rubber. Each carcass cord intersects the equatorial plane. In this tire 2, the angle formed by the carcass cords with respect to the equatorial plane is 70° or more and 90° or less. The carcass 12 of this tire 2 has a radial structure. In this tire 2, the material of the carcass cords is steel. A cord made of organic fibers may be used as the carcass cord.

In this tire 2 , the carcass ply 36 is folded back around each core 30 from the inner side to the outer side in the axial direction. The carcass ply 36 includes a main body portion 38 that bridges one core 30 and the other core 30, and a pair of pairs that are connected to the main body portion 38 and folded back around each core 30 from the inner side to the outer side in the axial direction. and a folded portion 40 . In this tire 2, the end 42 of the folded portion 40 is located radially inside the outer end 44 of the inner apex 32u.

The belt 14 is positioned radially inside the tread 4 . This belt 14 is located radially outside the carcass 12 .

The belt 14 is composed of a plurality of radially laminated layers 46 . The belt 14 of this tire 2 is composed of four layers 46 consisting of a first layer 46A, a second layer 46B, a third layer 46C and a fourth layer 46D. In this tire 2, the number of layers 46 forming the belt 14 is not particularly limited. The configuration of the belt 14 is appropriately determined in consideration of the specifications of the tire 2 .

In this tire 2, of the four layers 46, the second layer 46B positioned between the first layer 46A and the third layer 46C has the widest width in the axial direction. The radially outermost fourth layer 46D has the narrowest axial width. As shown in FIG. 1, the axial width of the third layer 46C is greater than the axial width of the first layer 46A. In this tire 2, the ends of the first layer 46A, the second layer 46B, the third layer 46C, and the fourth layer 46D, which constitute the belt 14, are axially positioned outside shoulder circumferential grooves, which will be described later.

FIG. 2 shows the structure of the belt 14 of the tire 2. As shown in FIG. In FIG. 2 , the horizontal direction is the axial direction of the tire 2 and the vertical direction is the circumferential direction of the tire 2 .

Each layer 46 that makes up the belt 14 includes a number of parallel belt cords 46c. The number of belt cords 46c in each layer 46 is 20 or more and 40 or less per width of 50 mm of this layer 46 in the cross section of this layer 46 along the plane perpendicular to the extending direction of this belt cord 46c. be. The belt cord 46c is covered with a topping rubber 46g. In this tire 2, the material of the belt cord 46c is steel. This belt cord 46c is a steel cord. In FIG. 2, for convenience of explanation, the belt cord 46c covered with the topping rubber 46g is represented by a solid line.

The belt cord 46c is inclined with respect to the circumferential direction. In this tire 2, each layer 46 forming the belt 14 includes a large number of belt cords 46c inclined with respect to the circumferential direction.

As shown in FIG. 2, the direction of inclination of the belt cords 46c of the first layer 46A with respect to the circumferential direction is the same as the direction of inclination of the belt cords 46c of the second layer 46B with respect to the circumferential direction. The direction of inclination of the belt cords 46c of the second layer 46B with respect to the circumferential direction is opposite to the direction of inclination of the belt cords 46c of the third layer 46C with respect to the circumferential direction. The direction of inclination of the belt cords 46c of the third layer 46C with respect to the circumferential direction is the same as the direction of inclination of the belt cords 46c of the fourth layer 46D with respect to the circumferential direction. The direction of inclination of the belt cords 46c of the first layer 46A with respect to the circumferential direction may be opposite to the direction of inclination of the belt cords 46c of the second layer 46B with respect to the circumferential direction. The direction of inclination with respect to the circumferential direction may be opposite to the direction of inclination with respect to the circumferential direction of the belt cords 46c of the third layer 46C.

In the present invention, among the plurality of layers constituting the belt, the layer having the widest width in the axial direction is the first reference layer, and the layer laminated outside the first reference layer is the second reference layer, The radially innermost layer is the third reference layer. As described above, in this tire 2, the belt 14 is composed of the radially laminated first layer 46A, second layer 46B, third layer 46C and fourth layer 46D. In this tire 2, the second layer 46B having the widest axial width among these layers 46 is the first reference layer B1, and the third layer 46C is laminated outside the second layer 46B in the radial direction. is the second reference layer B2. The first layer 46A located on the innermost side in the radial direction is the third reference layer B3. The fourth layer 46D is the fourth reference layer B4.

Each cushioning layer 16 is located between the belt 14 and the carcass 12 at the ends of the belt 14 . The cushion layer 16 is made of crosslinked rubber.

An inner liner 18 is positioned inside the carcass 12 . The inner liner 18 constitutes the inner surface of the tire 2 . This inner liner 18 is made of a crosslinked rubber having excellent air shielding properties. The inner liner 18 retains the internal pressure of the tire 2 .

Each steel reinforcing layer 20 is located in the bead 8 portion. The steel reinforcement layer 20 is folded axially inwardly outwardly around the core 30 along the carcass plies 36 . In this tire 2 , at least part of the steel reinforcing layer 20 is in contact with the carcass ply 36 . Although not shown, steel reinforcement layer 20 includes a large number of filler cords in parallel. The material of the filler cord is steel.

Each fiber reinforcement layer 21 is located axially outside the bead 8 and covers the ends of the axially outer portions of the steel reinforcement layers 20 . This fiber reinforcement layer 21 consists of two plies 47 . Although not shown, each ply 47 includes a number of side-by-side fiber cords. The fiber cords in the fiber reinforcing layer 21 are covered with a topping rubber. The textile cord consists of organic fibers. Nylon fibers are preferred as the organic fibers.

FIG. 3 shows a developed view of the tread surface 22. As shown in FIG. In FIG. 3 , the horizontal direction is the axial direction of the tire 2 and the vertical direction is the circumferential direction of the tire 2 . The direction perpendicular to the paper surface of FIG. 3 is the radial direction of the tire 2 .

In FIG. 3 , the symbol PE is the edge of the tread surface 22 . When the edge PE of the tread surface 22 cannot be identified visually, the tire 2 in a normal state is loaded with a normal load, the camber angle is set to 0°, and the tread 4 is brought into contact with a flat surface. An axially outer edge is defined as the edge PE of the tread surface 22 .

In this tire 2 , four circumferential grooves 24 are cut in the tread 4 . These circumferential grooves 24 are arranged in parallel in the axial direction and extend continuously in the circumferential direction.

Of the four circumferential grooves 24, the inner circumferential groove 24c in the axial direction, that is, the circumferential groove 24c near the equator PC is the center circumferential groove 24c. 24 s of circumferential grooves located on the outer side in the axial direction, that is, 24 s of circumferential grooves near the edge PE of the tread surface 22 are shoulder circumferential grooves 24 s. When the circumferential grooves 24 formed on the tread 4 include the circumferential grooves 24 positioned on the equator PC, the circumferential grooves 24 positioned on the equator PC are defined as the center circumferential grooves. Furthermore, when the circumferential groove 24 exists between the center circumferential groove 24c and the shoulder circumferential groove 24s, this circumferential groove 24 is defined as the middle circumferential groove.

In FIG. 3, a double arrow TW indicates the actual width of the tread. The actual width TW of the tread is represented by the distance from the edge PE of one tread surface 22 to the edge PE of the other tread surface 22 measured along the tread surface 22 . In FIG. 3, a double arrow GC indicates the actual width of the center circumferential groove 24c. A double arrow GS indicates the actual width of the shoulder circumferential groove 24s. Actual width GC and actual width GS are measured along a virtual tread surface obtained by assuming that tread surface 22 has no circumferential grooves 24 . In FIG. 1, a double arrow DC indicates the depth of the center circumferential groove 24c. A double arrow DS indicates the depth of the shoulder circumferential groove 24s.

In the tire 2, the actual width GC of the center circumferential groove 24c is preferably about 2 to 10% of the actual width TW of the tread from the viewpoint of contribution to drainage performance and traction performance. The depth DC of the center circumferential groove 24c is preferably 13 to 25 mm.

In this tire 2, the actual width GS of the shoulder circumferential groove 24s is preferably about 1 to 7% of the actual width TW of the tread from the viewpoint of contribution to drainage performance and traction performance. The depth DS of the shoulder circumferential groove 24s is preferably 13 to 25 mm.

As described above, in this tire 2 , four circumferential grooves 24 are cut in the tread 4 . Thus, the tread 4 has five land portions 26 . These land portions 26 are arranged in parallel in the axial direction and extend in the circumferential direction.

Of the five land portions 26, the land portion 26c located on the inner side in the axial direction, that is, the land portion 26c located on the equator PC is the center land portion 26c. The land portion 26s located on the outer side in the axial direction, that is, the land portion 26s including the edge PE of the tread surface 22 is the shoulder land portion 26s. Further, the land portion 26m positioned between the center land portion 26c and the shoulder land portion 26s is the middle land portion 26m. If the land portion 26 positioned axially inward among the land portions 26 formed in the tread 4 is positioned near the equator PC instead of on the equator PC, the land portion 26 is positioned near the equator PC. Let the land part 26 be a center land part.

In FIG. 3, a double arrow RC indicates the actual width of the center land portion 26c. A double arrow RS indicates the actual width of the shoulder land portion 26s. A double arrow RM indicates the actual width of the middle land portion 26m. Actual width RC, actual width RS and actual width RM are measured along tread surface 22 .

In this tire 2, the actual width RC of the center land portion 26c is preferably about 10 to 18% of the actual width TW of the tread from the viewpoint of steering stability and wet performance. From the same point of view, the actual width RM of the middle land portion 26m is preferably about 10 to 18% of the actual width TW of the tread.

As shown in FIG. 3, the center land portion 26c of the tire 2 is cut with a plurality of sipes 48c that cross the center land portion 26c. In the center land portion 26c, these sipes 48c are circumferentially spaced apart. The center land portion 26c intermittently extends in the circumferential direction. A plurality of sipes 48m crossing the middle land portion 26m are also cut into the middle land portion 26m. These sipes 48m are circumferentially spaced apart. Like the center land portion 26c, the middle land portion 26m also intermittently extends in the circumferential direction.

In this tire 2, the sipe 48c of the center land portion 26c and the sipe 48m of the middle land portion 26m contribute to improvement of wet performance. The width of these sipes 48 is set within a range of 0.5 mm or more and 1.5 mm or less. The depth of the sipe 48 is set within a range of 3 mm or more and 12 mm or less.

In this tire 2, unlike the center land portion 26c and the middle land portion 26m, the shoulder land portion 26s is not provided with sipes or narrow grooves crossing the shoulder land portion 26s. The shoulder land portion 26s continuously extends in the circumferential direction without interruption.

As shown in FIGS. 1 and 3 , in this tire 2 , a thin longitudinal groove 50 extending continuously in the circumferential direction may be further cut axially outward of the shoulder circumferential groove 24 s. As a result, a narrow land portion 52 is formed on the axially outer side of the shoulder land portion 26s. The narrow land portion 52 extends continuously in the circumferential direction. The narrow land portion 52 suppresses an excessive increase in ground contact pressure at the edge PE of the tread surface 22 . The narrow land portions 52 suppress the occurrence of uneven wear. From this point of view, the tire 2 has a narrow land portion 52 located outside the shoulder land portion 26s in the axial direction and extending in the circumferential direction. A groove 50 is preferred. In this case, the width of the narrow land portion 52 is usually set within a range of 3 mm or more and 7 mm or less. A portion consisting of the tread 4, the thin longitudinal grooves 50 and the thin land portions 52 constitutes the tread portion. A tread 4 and a thin land portion 52 positioned axially outside of the tread 4 are formed by forming the thin vertical grooves 50 in the end portion of the tread portion.

In FIG. 1 , a double-headed arrow DT indicates the depth of the thin longitudinal groove 50 . In FIG. 3 , a double-headed arrow GT indicates the actual width of the thin longitudinal groove 50 . In this tire 2, the actual width GT of the thin longitudinal groove 50 is set to 30% or less of the actual width GS of the shoulder circumferential groove 24s. The depth DT of the thin longitudinal groove 50 is set in the range of 0.6 to 1.0 times the depth DS of the shoulder circumferential groove 24s.

FIG. 4 shows part of the profile of the tread surface 22 of tire 2 . In FIG. 4 , the horizontal direction is the axial direction of the tire 2 and the vertical direction is the radial direction of the tire 2 . The direction perpendicular to the paper surface of FIG. 4 is the circumferential direction of the tire 2 .

This profile is a state (hereinafter also referred to as a reference state) in which the tire 2 is mounted on a rim R (that is, a normal rim), the internal pressure of the tire 2 is adjusted to 10% of the normal internal pressure, and no load is applied to the tire 2. ) of this tire 2 along a plane containing the axis of rotation. The profile in this reference state corresponds to the profile of the cavity surface of the mold, which will be described later.

The tread surface 22 has a radially outwardly convex profile. The profile of this tread surface 22 is symmetrical with respect to the equatorial plane. The tread surface 22 of this tire 2 is divided into at least three zones in the axial direction. The tread surface 22 includes a crown portion 54c and a pair of side portions 54s.

The crown portion 54c is located at the center in the axial direction. This crown portion 54c includes the equator PC. In this tire 2, the profile of the crown portion 54c is represented by an arc having a radius Rc. Although not shown, the center of this arc is located on the equatorial plane.

The side portion 54s is located outside the crown portion 54c in the axial direction. The side portion 54 s includes the edge PE of the tread surface 22 . In this tire 2, the profile of the side portion 54s is represented by an arc having a radius Rs.

In FIG. 4, symbol Pcs is the boundary between the crown portion 54c and the side portion 54s. The arc representing the profile of the crown portion 54c (hereinafter also referred to as the crown arc) contacts the arc representing the profile of the side portion 54s (hereinafter also referred to as the side arc) at this boundary Pcs.

In this tire 2, the boundary Pcs coincides with the inner edge 56u of the shoulder land portion 26s. The profile of the tread surface 22 may be configured such that the boundary Pcs coincides with the outer edge 58s of the middle land portion 26m, and the boundary Pcs is formed between the inner edge 56u of the shoulder land portion 26s and the outer edge 58s of the middle land portion 26m. The profile of this tread surface 22 may be configured to lie between. The profile of the tread surface 22 may be configured such that the boundary Pcs is located on the outer surface of the middle land portion 26m, and the tread surface is configured such that the boundary Pcs is located on the outer surface of the shoulder land portion 26s. Twenty-two profiles may be configured.

In this tire 2, the radius Rc of the arc representing the profile of the crown portion 54c is specified as follows. First, a virtual arc (hereinafter also referred to as a first virtual arc ) is drawn. Between the outer edge 60s of one center land portion 26c and the outer edge 60s of the other center land portion 26c, the deviation between the trajectory represented by the first virtual arc and the profile of the crown portion 54c is the first virtual Measured along the normal of the arc. When this deviation is within 3% of the length of the line connecting the outer edge 60s of one center land portion 26c and the outer edge 60s of the other center land portion 26c, the radius of this first virtual arc is equal to the crown portion. It is identified as the radius Rc of the arc representing the profile of 54c. If there is a groove between the outer edge 60s of one center land portion 26c and the outer edge 60s of the other center land portion 26c, the virtual profile obtained assuming that there is no such groove is the crown portion 54c. Used as a profile.

In this tire 2, the radius Rs of the arc representing the profile of the side portion 54s is specified as follows. First, the boundary Pcs is identified using the aforementioned first virtual arc. Specifically, the end of the tangential line between the profile of the tread surface 22 and the first virtual arc or the intersection of the profile of the tread surface 22 and the first virtual arc is specified as the boundary Pcs. Next, another virtual arc (hereinafter referred to as Also called a second virtual arc.) is drawn. Between the boundary Pcs and the edge PE of the tread surface 22, the deviation between the trajectory represented by this second virtual arc and the profile of the side portion 54s is measured along the normal line of this second virtual arc. When this deviation is within 3% of the length of the line segment connecting the boundary PCS and the edge PE of the tread surface 22, the radius of this second virtual arc is specified as the radius Rs of the arc representing the profile of the side portion 54s. be done. Note that if there is a groove between the boundary Pcs and the edge PE of the tread surface 22, a virtual profile obtained assuming that there is no such groove is used as the profile of the side portion 54s.

Next, a method for manufacturing this tire 2 will be described. In this method of manufacturing the tire 2, a preform for the constituent members of the tire 2 such as the tread 4 and the sidewall 6 is prepared. For example, for the tread 4, a tread sheet as a preform of the tread 4 is prepared by processing the rubber composition for the tread 4 into a sheet and cutting the sheet into a predetermined length. For the layer 46 constituting the belt 14, a mother sheet is prepared by sandwiching the parallel belt cords 46c between two topping sheets, and then the mother sheet is cut diagonally with respect to the length direction. A belt sheet as a preform for the layer 46 is prepared by the above.

In this tire 2 manufacturing method, preforms for constituent members of the tire 2 are assembled in a molding machine (not shown). For example, after the carcass ply 36 is obtained by processing a carcass sheet as a preform of the carcass ply 36 into a tubular shape, a belt sheet is wound around the tubular carcass sheet at a position where the belt 14 is formed. Layer 46 is obtained by joining one end of the belt sheet to the other. After forming the belt 14 by winding the four belt sheets, a tread sheet is wound on the belt 14 . The tread 4 is obtained by joining one end and the other end of the tread sheet. By combining the preforms in this way, the uncrosslinked tire 2, that is, the raw tire 2r is obtained. The manufacturing method of this tire 2 includes a step of preparing a green tire 2r including a tread 4 and a belt 14. As shown in FIG.

In this method of manufacturing the tire 2, the green tire 2r is put into a mold set at a predetermined temperature. The bladder expanded by the filling of the heating medium presses the green tire 2r against the cavity surface of the mold from the inside. The raw tire 2r is pressurized and heated in the mold for a predetermined time. As a result, the rubber composition of the raw tire 2r is crosslinked, and the tire 2 is obtained. This tire 2 is obtained by vulcanizing and molding a raw tire 2r. This tire 2 is a vulcanization product of a raw tire 2r.

As described above, the raw tire 2r put into the mold is pressed against the mold by the inflated bladder from the inside. At this time, the raw tire 2r is expanded in diameter and stretched in the circumferential direction. That is, the tire 2 is formed by putting the raw tire 2r into a mold, expanding the diameter of the raw tire 2r in the mold, and pressurizing and heating the raw tire 2r. The manufacturing method of the tire 2 includes a step of putting the raw tire 2r into a mold, and a step of expanding the diameter of the raw tire 2r in the mold and pressurizing and heating the raw tire 2r.

The belt 14 of the tire 2 is stretched when the green tire 2r is expanded. In this tire 2, the stretch of the belt 14, specifically , the stretch of the belt 14 at the ends of the belt 14 (hereinafter also referred to as the belt edges), and the stretch of the belt 14 at the center of the belt 14 (hereinafter also referred to as the belt center); is identified. In the present invention, the stretch of the belt 14 is specified based on the radially innermost first layer 46A of the layers 46 constituting the belt 14, ie, the third reference layer B3.

The left side of FIG. 5 shows the state of the belt 14 in the uncrosslinked tire 2, ie, the green tire 2r, before being put into the mold. The right side of FIG. 5 shows the state of the belt 14 in the mold M of the tire 2 obtained by pressurizing and heating the raw tire 2r. The member designated BD is the inflated bladder. This state of the right tire 2 corresponds to a state in which the tire 2 is mounted on a rim R (normal rim), the internal pressure is adjusted to 10% of the normal internal pressure, and no load is applied.

In FIG. 5, the arrow indicated by symbol Rcb is the inner diameter of the central portion of the third reference layer B3 in the raw tire 2r. The inner diameter Rcb is represented by the radial distance of the inner peripheral surface of the third reference layer B3 on the equatorial plane of the raw tire 2r from the central axis (not shown) of the raw tire 2r. The arrow indicated by symbol Rsb is the inner diameter of the end portion of the third base layer B3 in the raw tire 2r. The inner diameter Rsb is represented by the radial distance of the inner peripheral surface of the third reference layer B3 at the edge of the third reference layer B3 of the raw tire 2r from the central axis of the raw tire 2r.

In FIG. 5 , the arrow indicated by symbol Rca is the inner diameter of the central portion of the third reference layer B3 in the tire 2 . The inner diameter Rca is represented by the radial distance of the inner peripheral surface of the third reference layer B3 on the equatorial plane of the tire 2 from the central axis of the tire 2 . The arrow indicated by symbol Rsa is the inner diameter of the end portion of the third reference layer B3 in the tire 2 . This inner diameter Rsa is represented by the radial distance from the central axis of the tire 2 to the inner peripheral surface of the third reference layer B3 at the end of the third reference layer B3 of the tire 2 .

In the present invention, the stretch of the belt 14 at the end of the third reference layer B3, that is, the shoulder stretch Ss is expressed by the following formula (1). This shoulder stretch Ss is an index of the stretch of the belt 14 at the belt end.
(shoulder stretch) 100×(Rsa-Rsb)/Rsb (1)

The stretch of the belt 14 at the center of the third reference layer B3, that is, the center stretch Sc is given by the following formula (2). This center stretch Sc is an index of the stretch of the belt 14 at the center of the belt.
(Center stretch) 100×(Rca-Rcb)/Rcb (2)

There is a radial runout (hereinafter also referred to as RRO) as an index representing the vertical runout of the tire 2 . In the present invention, by measuring this RRO, it is possible to ascertain the state of occurrence of a portion (for example, irregularities) that may become a starting point of uneven wear.

In this tire 2, as will be described later, in order to suppress the occurrence of uneven wear, the stretch of the belt center and the stretch of the belt end when the raw tire 2r is pressurized and heated in the mold M are defined. As a result, the RRO at the equatorial portion of the tread 4, ie, the center portion C, and the RRO at the edge portion, ie, the shoulder portion S, of the tread 4 are controlled.

In the present invention, the RRO at the center portion C is measured at the axial center of the center land portion 26c (the equator PC in this tire 2), more specifically, within a range of ±10 mm from this center. As the RRO of the shoulder portion S, the RRO is measured at the center of the shoulder land portion 26s in the axial direction, specifically within a range of ±10 mm from this center. This RRO measurement is performed using a uniformity tester in accordance with the test conditions of JASO C607:2000 "Uniformity test method for automobile tires".

In this tire 2, the ratio of the center stretch Sc represented by the above formula (2) to the shoulder stretch Ss represented by the above formula (1) is 1 or more and 3 or less.

In this tire 2, the ratio of the center stretch Sc to the shoulder stretch Ss is set to 1 or more, so that the belt 14 is sufficiently stretched during vulcanization molding. Therefore, in this tire 2, a small RRO is obtained in each of the center portion C and the shoulder portion S. In this tire 2, the tread 4 is less likely to have a portion (eg, irregularities) that may cause uneven wear (eg, drop-off wear of the shoulder land portion 26s). By setting this ratio to 3 or less, the tire 2 is obtained in which the absolute value of the difference between the overall RRO value at the center portion C and the overall RRO value at the shoulder portion S is small. In this case as well, the tread 4 is less likely to be the starting point of uneven wear.

Furthermore, in this tire 2, the shoulder stretch Ss is 1% or more. This provides sufficient stretching of the belt ends. In this tire 2, the RRO at the belt end is kept small. Therefore, even when the tire 2 is inflated, the RRO at the shoulder portion S of the tread 4 is kept small. In this tire 2 , the tread 4 is less likely to be the starting point of uneven wear. From this point of view, the shoulder stretch Ss is preferably 1.3% or more.

In this tire 2, the ratio of the center stretch Sc to the shoulder stretch Ss is 1 or more and 3 or less, and the shoulder stretch Ss is 1% or more. As a result, in the tire 2, the RRO at the center portion C of the tread 4 and the RRO at the shoulder portions S of the tread 4 are well balanced. In this tire 2 , the tread 4 is less prone to wear. In this tire 2, the occurrence of uneven wear is suppressed.

In this tire 2, the shoulder stretch Ss is preferably 2.5% or less. As a result, in the tire 2, the belt ends are appropriately stretched, and the flow of the rubber is controlled so that the rubber flows uniformly in the circumferential direction during this stretch. In this tire 2, a small RRO is obtained at the shoulder portion S. In this tire 2 , the tread 4 is less likely to be the starting point of uneven wear. From this point of view, the shoulder stretch Ss is more preferably 2% or less.

In this tire 2, the center stretch Sc is preferably 2% or more. As a result, the central portion of the belt is sufficiently stretched. In this tire 2, the RRO at the center of the belt is kept small. Therefore, even when the tire 2 is inflated, the RRO at the center portion C of the tread 4 is kept small. In this tire 2 , the tread 4 is less likely to be the starting point of uneven wear. From this point of view, the center stretch Sc is more preferably 2.5% or more.

In this tire 2, the center stretch Sc is preferably 3.5% or less. As a result, in the tire 2, the central portion of the belt 14 is appropriately stretched, and during this stretching, the flow of the rubber is controlled so that the rubber flows uniformly in the circumferential direction. In this tire 2, a small RRO is obtained at the center portion C. In this tire 2 , the tread 4 is less likely to be the starting point of uneven wear.

In the tire 2, from the viewpoint of effectively suppressing the occurrence of uneven wear, it is more preferable that the center stretch Sc is 2% or more and the shoulder stretch Ss is 1% or more. More preferably, the tire 2 has a center stretch Sc of 2.5% or more and 3.5% or less, and a shoulder stretch Ss of 1.3% or more and 2.5% or less. In this tire 2, it is particularly preferable that the center stretch Sc is 2.5% or more and 3.5% or less and the shoulder stretch Ss is 1.3% or more and 2.0% or less.

As described above, the layer 46 constituting the belt 14 is obtained by winding a belt sheet around a cylindrical carcass sheet and joining one end and the other end of the belt sheet. In this layer 46 there is a joint portion of the belt sheet. When the belt 14 is stretched during vulcanization, this joint portion is also stretched. As described above, in this tire 2, the RRO is controlled by stretching the belt 14. FIG. However, since the speed of stretching, the flexibility of the rubber during stretching, etc., affect the flow of the rubber, it is preferable that the RRO is also within a predetermined range in order to effectively suppress the occurrence of uneven wear.

In this tire 2, the overall RRO value at the center portion C of the tread 4 is preferably 1.5 mm or less, and the overall RRO value at the shoulder portions S is preferably 1.5 mm or less. As a result, the out-of-roundness of the tire 2 is improved, and the formation of starting points of uneven wear is suppressed. In this tire 2, the occurrence of uneven wear is effectively suppressed.

In this tire 2, the absolute value of the difference between the overall RRO value at the center portion C and the overall RRO value at the shoulder portion S is preferably 0.5 mm or less. As a result, the amount of camber of the tire 2 is appropriately maintained, so that the difference between the contact length of the center portion C and the contact length of the shoulder portion S is suppressed. Since the shoulder portion S, ie, the shoulder land portion 26s, is prevented from slipping on the road surface, the tire 2 is effectively prevented from uneven wear.

In this tire 2, the absolute value of the difference between the RRO at the center portion C and the RRO at the shoulder portion S at each circumferential portion of the tread 4 is preferably 0.20 mm or less. As a result, the RRO at the center portion C and the RRO at the shoulder portion S are interlocked at each portion in the circumferential direction of the tread 4, thereby suppressing variations in the degree of slippage of the shoulder land portion 26s on the road surface. In this tire 2, the occurrence of uneven wear is effectively suppressed. The absolute value of the difference between the RRO at the center portion C and the RRO at the shoulder portion S at each portion in the circumferential direction of the tread 4 is specified in the cross section of the tire 2 along the plane including the central axis of the tire 2. It is calculated based on the RRO of the center portion C and the RRO of the shoulder portion S, which are calculated. Further, each portion in the circumferential direction of the tread 4 means positions on the tread surface 22 (eight test positions in total) specified at 45° intervals around the central axis of the tire 2 .

As described above, in this tire 2, the tread 4 is provided with at least three circumferential grooves 24 extending continuously in the circumferential direction. and an outwardly located shoulder circumferential groove 24s.

In this tire 2, the shoulder circumferential grooves 24s are preferably narrower than the center circumferential grooves 24c. Thereby, the actual width RS of the shoulder land portion 26s is sufficiently secured. Since the shoulder land portion 26s has appropriate rigidity, the shoulder land portion 26s is less likely to be worn. In this tire 2, uneven wear (for example, uneven wear in which the entire shoulder land portion 26s is worn) is effectively suppressed. From this point of view, the ratio of the actual width GS of the shoulder circumferential grooves 24s to the actual width GC of the center circumferential grooves 24c is preferably 0.9 or less. From the viewpoint of maintaining good drainage properties, this ratio is preferably 0.7 or more.

As described above, in the tire 2, at least three circumferential grooves 24 are formed in the tread 4, thereby forming at least four land portions 26 in the tread 4. These land portions 26 extend axially. center land portion 26c located inside and shoulder land portion 26s located outside.

In this tire 2, the actual width RS of the shoulder land portion 26s is preferably wider than the actual width RC of the center land portion 26c. In this tire 2, the rigidity of the shoulder land portion 26s is sufficiently ensured. Since the shoulder land portion 26s has appropriate rigidity, the shoulder land portion 26s is less likely to be worn. In this tire 2, uneven wear (for example, uneven wear in which the entire shoulder land portion 26s is worn) is effectively suppressed.

In this tire 2, the ratio of the width RS of the shoulder land portion 26s to the width RC of the center land portion 26c is preferably 1.15 or more and preferably 1.45 or less. By setting this ratio to 1.15 or more, the rigidity of the shoulder land portion 26s is sufficiently ensured. Since the shoulder land portion 26s has appropriate rigidity, the shoulder land portion 26s is less likely to be worn. In this tire 2, uneven wear (for example, uneven wear in which the entire shoulder land portion 26s is worn) is effectively suppressed. From this point of view, this ratio is more preferably 1.20 or more. By setting this ratio to 1.45 or less, the circumferential length difference in the shoulder land portion 26s is appropriately maintained. In this tire 2, since the shoulder land portions 26s are less likely to have different slips on the road surface, the shoulder land portions 26s are prevented from being worn down. Even in this case, the tire 2 can effectively suppress uneven wear. From this point of view, this ratio is more preferably 1.40 or less.

In this tire 2, the ratio of the actual width RM of the middle land portion to the actual width RC of the center land portion 26c is preferably 0.95 or more and preferably 1.05 or less. By setting this ratio to 0.95 or more, the actual width RS of the shoulder land portion 26s is appropriately secured, so that the circumferential length difference in the shoulder land portion 26s is appropriately maintained. In this tire 2, since the shoulder land portions 26s are less likely to have different slips on the road surface, the shoulder land portions 26s are prevented from being worn down. In this tire 2, the occurrence of uneven wear is effectively suppressed. By setting this ratio to 1.05 or less, the actual width RS of the shoulder land portion 26s is ensured, and the shoulder land portion 26s has sufficient rigidity. Since the shoulder land portions 26s are less likely to be worn, in the tire 2, uneven wear (for example, uneven wear in which the entire shoulder land portions 26s are worn) is effectively suppressed.

As described above, in this tire 2, the ratio of the center stretch Sc to the shoulder stretch Ss is 1 or more and 3 or less, and the shoulder stretch Ss is 1% or more. In this tire 2, the degree of stretch at the ends and center of the belt 14 is well balanced. This stretch control effectively suppresses disorder of the arrangement of the belt cords 46c in each layer 46 constituting the belt 14. FIG.

In FIG. 2, an angle Bc is an angle of inclination of the belt cords 46c included in the second layer 46B, that is, the first reference layer B1, with respect to the circumferential direction on the equatorial plane. The angle Be is an inclination angle formed by the belt cord 46c included in the first reference layer B1 with respect to the circumferential direction at the layer end. The angle Cc is the angle of inclination of the third layer 46C, ie, the belt cord 46c included in the second reference layer B2, with respect to the circumferential direction on the equatorial plane. The angle Ce is an inclination angle formed by the belt cord 46c included in the second reference layer B2 with respect to the circumferential direction at the layer end. The angle Ac is the inclination angle formed by the belt cords 46c included in the first layer 46A, that is, the third reference layer B3, with respect to the circumferential direction on the equatorial plane. The angle Ae is the inclination angle of the belt cord 46c included in the third reference layer B3 with respect to the circumferential direction at the layer edge. The angle Dc is the angle of inclination of the belt cords 46c included in the fourth layer 46D, that is, the fourth reference layer B4, with respect to the circumferential direction on the equatorial plane. The angle De is the inclination angle of the belt cord 46c included in the fourth reference layer B4 with respect to the circumferential direction at the layer end. The angle of inclination of the belt cord 46c on the equatorial plane is represented by the angle of inclination of the belt cord 46c positioned within a range of 10 mm width centered on the equatorial plane. The inclination angle of the belt cord 46c at the layer end is represented by the inclination angle of the belt cord 46c located within a range of 10 mm inside from the edge of each layer.

In this tire 2, preferably, in the first reference layer B1, the inclination angle Be at the layer end portion of the belt cord 46c is equal to the inclination angle Bc at the equatorial plane. In other words, the difference (Be-Bc) between the inclination angle Be at the layer end of the belt cord 46c and the inclination angle Bc at the equator plane is preferably -0.4° or more and 0.4° or less. In this tire 2, the first reference layer B1, which had a difference (Be-Bc) of 2° or more and tended to have lower rigidity at the ends, has substantially uniform rigidity in the axial direction. A decrease in rigidity at the end portion is suppressed, and the binding force of the first reference layer B1 is less likely to be biased, so the belt 14 including the first reference layer B1 contributes to suppression of uneven wear. In this tire 2, uneven wear is less likely to occur.

In this tire 2, preferably, in the second reference layer B2, the inclination angle Ce at the layer end portion of the belt cord 46c is equal to the inclination angle Cc at the equatorial plane. In other words, the difference (Ce-Cc) between the inclination angle Ce at the layer end of the belt cord 46c and the inclination angle Cc at the equator plane is preferably -0.4° or more and 0.4° or less. In this tire 2, the second reference layer B2, which had a difference (Ce-Cc) of 2° or more and tended to have lower rigidity at the ends, has substantially uniform rigidity in the axial direction. A decrease in rigidity at the end portion is suppressed, and the binding force of the second reference layer B2 is less likely to be biased, so the belt 14 including the second reference layer B2 contributes to suppression of uneven wear. In this tire 2, uneven wear is less likely to occur.

In this tire 2, preferably, in the third reference layer B3, the inclination angle Ae at the layer end portion of the belt cord 46c is equal to the inclination angle Ac at the equatorial plane. In other words, the difference (Ae-Ac) between the inclination angle Ae at the layer end of the belt cord 46c and the inclination angle Ac at the equator plane is preferably -0.4° or more and 0.4° or less. In this tire 2, the third reference layer B3, which had a difference (Ae-Ac) of 2° or more and tended to have lower rigidity at the ends, has substantially uniform rigidity in the axial direction. A decrease in rigidity at the end portion is suppressed, and the binding force of the third reference layer B3 is less likely to be biased, so the belt 14 including the third reference layer B3 contributes to suppression of uneven wear. In this tire 2, uneven wear is less likely to occur.

In this tire 2, preferably, in the fourth reference layer B4, the inclination angle De at the layer end portion of the belt cord 46c is equal to the inclination angle Dc at the equatorial plane. In other words, the difference (De-Dc) between the inclination angle De at the layer end of the belt cord 46c and the inclination angle Dc at the equator plane is preferably -0.4° or more and 0.4° or less. In this tire 2, the fourth reference layer B4, which had a difference (De-Dc) of 2° or more and tended to have lower rigidity at the ends, has substantially uniform rigidity in the axial direction. A decrease in rigidity at the end portion is suppressed, and the binding force of the fourth reference layer B4 is less likely to be biased, so the belt 14 including the fourth reference layer B4 contributes to suppression of uneven wear. In this tire 2, uneven wear is less likely to occur.

In this tire 2, from the viewpoint of effectively suppressing the occurrence of uneven wear, at least in the first reference layer B1 of the layers 46 constituting the belt 14, the inclination angle at the layer end of the belt cord 46c is It is preferably equal to the tilt angle. Among the layers 46 constituting the belt 14, in the first reference layer B1 and the second reference layer B2, the inclination angle of the belt cords 46c at the layer ends is more preferably equal to the inclination angle on the equatorial plane. In all the layers 46 constituting the belt 14, it is more preferable that the inclination angle at the layer end of the belt cord 46c is equal to the inclination angle at the equatorial plane.

In the tire 2, the inclination angle Bc of the belt cord 46c on the equatorial plane is preferably 12° or more and 20° or less in the first reference layer B1. This inclination angle Bc is smaller than that of the conventional tire belt. The binding force of a belt including this first reference layer B1 is higher than that of a conventional belt. This belt 14 contributes to suppression of uneven wear. From this point of view, the inclination angle Bc is preferably 14° or more and preferably 18° or less.

In this tire 2, the inclination angle Cc of the belt cord 46c on the equatorial plane is preferably 12° or more and 20° or less in the second reference layer B2. This inclination angle Cc is smaller than that of the conventional tire belt. The binding force of a belt containing this second reference layer B2 is higher than that of a conventional belt. This belt 14 contributes to suppression of uneven wear. From this point of view, the inclination angle Cc is preferably 14° or more and preferably 18° or less.

In this tire 2, in order to properly maintain the rigidity of the belt 14, the inclination angle Ac of the belt cords 46c of the third reference layer B3 and the inclination angle Dc of the belt cords 46c of the fourth reference layer B4 on the equatorial plane are: It is set at an angle larger than the inclination angle Bc of the belt cords 46c of the first reference layer B1 and the inclination angle Cc of the belt cords 46c of the second reference layer B2. Specifically, the inclination angle Ac of the belt cords 46c of the third reference layer B3 on the equator plane is preferably 50° or more and preferably 70° or less. The inclination angle Dc of the belt cords 46c of the fourth reference layer B4 on the equator plane is preferably 15° or more and preferably 35° or less.

In this tire 2, each layer 46 constituting the belt 14 is preferably configured such that the density of the belt cords 46c at the equatorial plane is equal to the density of the belt cords 46c at the layer ends. In this tire 2, the density of the end portion of the belt 14 has been reduced, and the rigidity of the belt 14 has tended to be reduced at the end portion, but has substantially uniform rigidity in the axial direction. Since the binding force of the belt 14 is less likely to be biased, the belt 14 contributes to the suppression of uneven wear. In this tire 2, uneven wear is less likely to occur. The density of the belt cords 46c is represented by the number of belt cords 46c present per 50 mm length of each layer in the circumferential direction.

In this tire 2, from the viewpoint of effectively suppressing the occurrence of uneven wear, at least the first reference layer B1 among the layers 46 constituting the belt 14 has the density of the belt cords 46c on the equatorial plane and the belt It is preferably configured to have the same density as the cord 46c. Among the layers 46 constituting the belt 14, the first reference layer B1 and the second reference layer B2 are configured so that the density of the belt cords 46c on the equatorial plane is equal to the density of the belt cords 46c on the layer ends. is more preferred. More preferably, all the layers 46 forming the belt 14 are constructed so that the density of the belt cords 46c at the equatorial plane is equal to the density of the belt cords 46c at the layer ends.

In this tire 2, the tread surface 22 includes a crown portion 54c having a profile represented by an arc having a radius Rc, and side portions 54s having a profile represented by an arc having a radius Rs. In this tire 2, the radius Rs of the arc representing the profile of the side portion 54s is preferably larger than the radius Rc of the arc representing the profile of the crown portion 54c. In this tire 2, the difference in circumference between the circumference of the equator portion and the circumference of the edge PE of the tread surface 22 is appropriately maintained. is suppressed. In this tire 2, the occurrence of uneven wear such as uneven wear is suppressed. From this point of view, the ratio of the radius Rs of the arc representing the profile of the side portion 54s to the radius Rc of the arc representing the profile of the crown portion 54c is preferably 1.1 or more and preferably 1.4 or less. From a similar point of view, the radius Rc of the arc representing the profile of the crown portion 54c is preferably 700 mm or more, and preferably 900 mm or less.

FIG. 6 shows part of the cross-section of this tire 2 shown in FIG. 6, the horizontal direction is the axial direction of the tire 2, and the vertical direction is the radial direction of the tire 2. As shown in FIG. The direction perpendicular to the paper surface of FIG. 6 is the circumferential direction of the tire 2 .

In FIG. 6( a ), an arrow WT indicates the axial width of the tread surface 22 . This axial direction WT is represented by the axial distance from one end PE of the tread surface 22 to the other end PE. Arrow W1 is the axial width of the second layer 46B as the first reference layer B1. This axial width W1 is represented by the axial distance from one end of the second layer 46B to the other end. Arrow W2 is the axial width of the third layer 46C as the second reference layer B2. This axial width W2 is represented by the axial distance from one end of the third layer 46C to the other end.

In this tire 2 the axial width W1 of the first reference layer B1 is preferably equal to or narrower than the axial width WT of the tread surface 22 . In this tire 2, the binding force of the belt 14 to the shoulder land portion 26s is appropriately maintained. With regard to the tire 2 circumference, since the circumference difference between the circumference of the equator portion and the circumference of the edge PE portion of the tread surface 22 is appropriately maintained, the shoulder land portion 26s is prevented from slipping on the road surface. In this tire 2, the occurrence of uneven wear such as uneven wear is suppressed.

In this tire 2, the ratio of the axial width W1 of the first reference layer B1 to the axial width WT of the tread surface 22 is preferably 0.85 or more and preferably 1.00 or less.

By setting the ratio of the axial width W1 of the first reference layer B1 to the axial width WT of the tread surface 22 to be 0.85 or more, the belt 14 sufficiently restrains the entire tread 4 . In this tire 2, the outer edge portion of the shoulder land portion 26s, that is, the end PE portion of the tread surface 22, is suppressed from peculiar dimensional growth, so that the shoulder land portion 26s is prevented from being worn down. In this tire 2, the occurrence of uneven wear is suppressed. From this point of view, this ratio is more preferably 0.90 or more, more preferably 0.92 or more.

By setting the ratio of the axial width W1 of the first reference layer B1 to the axial width WT of the tread surface 22 at 1.00 or less, the binding force of the belt 14 to the shoulder land portion 26s is appropriately maintained. With regard to the tire 2 circumference, since the circumference difference between the circumference of the equator portion and the circumference of the edge PE portion of the tread surface 22 is appropriately maintained, the shoulder land portion 26s is prevented from slipping on the road surface. In this tire 2, the occurrence of uneven wear such as uneven wear is suppressed. From this point of view, this ratio is preferably 0.97 or less, more preferably 0.95 or less.

In this tire 2, the ratio of the axial width W2 of the second reference layer B2 to the axial width WT of the tread surface 22 is preferably 0.80 or more. This second reference layer B2 contributes to the restraint of the tread 4. In this tire 2, since the belt 14 sufficiently restrains the entire tread 4, peculiar dimensional growth at the outer edge portion of the shoulder land portion 26s is suppressed. In this tire 2, the occurrence of uneven wear such as shoulder drop wear is suppressed. From this point of view, this ratio is more preferably 0.85 or more, more preferably 0.90 or more.

In this tire 2, the edge of the second reference layer B2 is located inside the edge of the first reference layer B1 in the axial direction. Since the edge of the second reference layer B2 and the edge of the first reference layer B1 do not coincide in the axial direction, concentration of strain on the edge of the belt 14 is prevented. In this tire 2, damage such as looseness is less likely to occur at the end of the belt 14. As shown in FIG. Moreover, the restraining force of the belt 14 on the shoulder land portion 26s is appropriately maintained, and the difference in the circumference between the circumference of the equator portion and the circumference of the end PE of the tread surface 22 with respect to the circumference of the tire 2 is is properly maintained. Since the shoulder land portion 26s is prevented from slipping on the road surface, the tire 2 is prevented from uneven wear such as uneven wear.

In FIG. 6(a), the double arrow D is the axial distance from the end of the second layer 46B as the first reference layer B1 to the end of the third layer 46C as the second reference layer B2.

In this tire 2, the axial distance D from the end of the first reference layer B1 to the end of the second reference layer B2 is preferably 3 mm or more, and preferably 8 mm or less.

By setting the distance D to 3 mm or more, the end of the second reference layer B2 and the end of the first reference layer B1 are arranged with an appropriate gap in the axial direction. Since the concentration of strain on the end portion of the belt 14 is suppressed, the tire 2 is prevented from being damaged at the end portion of the belt 14 such as looseness. From this point of view, the distance D is more preferably 4 mm or more.

By setting the distance D to 8 mm or less, the belt 14 sufficiently restrains the entire tread 4 . Since the peculiar dimensional growth in the outer edge portion of the shoulder land portion 26s is suppressed, in this tire 2, the shoulder land portion 26s is prevented from being worn down. From this point of view, the distance D is more preferably 7 mm or less.

In FIG. 6A, the double arrow Y is the distance from the third layer 46C at the end of the third layer 46C as the second reference layer B2 to the second layer 46B as the first reference layer B1. This distance Y is measured along the normal to the outer surface of the second layer 46B.

In this tire 2, the distance Y from the second reference layer B2 to the first reference layer B1 at the end of the second reference layer B2 is preferably 2.5 mm or more, and preferably 4.0 mm or less.

By setting the distance Y to 2.5 mm or more, the end of the second reference layer B2 is arranged with a sufficient distance from the end of the first reference layer B1. In this tire 2 , concentration of strain on the end portion of the belt 14 is sufficiently suppressed while securing the binding force of the belt 14 with respect to the tread 4 . In this tire 2, the occurrence of uneven wear is suppressed while preventing the occurrence of damage at the ends of the belt 14. FIG. From this point of view, the distance Y is more preferably 3.0 mm or more.

By setting the distance Y to 4.0 mm or less, the end portion of the second reference layer B2 is arranged with an appropriate distance from the tread surface 22 . Since the increase in ground contact pressure caused by the proximity of the end portion of the second reference layer B2 to the tread surface 22 is suppressed, in this tire 2, the shoulder land portion 26s is prevented from being worn such as stepped wear. be. Furthermore, since the edge of the second reference layer B2 is prevented from sagging, the movement of the edge of the second reference layer B2 is suppressed. Since the heat generation associated with the movement of the end portion is suppressed, the occurrence of damage such as looseness is prevented. From this point of view, the distance Y is more preferably 3.5 mm or less.

As shown in FIG. 6, the ends of the second layer 46B and the third layer 46C are each covered with a rubber layer 62. As shown in FIG. Two more rubber layers 62 are arranged between each end covered with the rubber layer 62 . In this tire 2, an edge member 64 made up of a total of four rubber layers 62 is sandwiched between the end of the second layer 46B and the end of the third layer 46C. As a result, the end portion of the third layer 46C is pushed up radially outward and separated from the end portion of the second layer 46B. This edge member 64 is made of crosslinked rubber. The aforementioned distance Y is also the thickness of this edge member 64 .

In FIG. 6A, a double arrow W4 indicates the axial width of the fourth layer 46D that constitutes the belt 14. In FIG. This axial width W4 is represented by the axial distance from one end of the fourth layer 46D to the other end.

In this tire 2, the ratio of the axial width W4 of the fourth layer 46D to the axial width WT of the tread surface 22 is preferably 0.67 or more. Thereby, the fourth layer 46</b>D contributes to restraining the tread 4 . In this tire 2, since the belt 14 sufficiently restrains the entire tread 4, peculiar dimensional growth at the outer edge portion of the shoulder land portion 26s is suppressed. In addition to appropriately maintaining the binding force of the belt 14 on the shoulder land portion 26s, regarding the circumference of the tire 2, the circumference difference between the circumference of the equator portion and the circumference of the end PE of the tread surface 22 is appropriate. This ratio is preferably 0.75 or less from the viewpoint of being maintained at .

In FIG. 6(b), reference P1 is the intersection of the tread surface 22 and a straight line passing through the end of the second layer 46B as the first reference layer B1 and extending in the radial direction. This intersection point P1 is a position on the tread surface 22 corresponding to the edge of the first reference layer B1. Reference P2 is the intersection of the tread surface 22 and a straight line passing through the end of the third layer 46C as the second reference layer B2 and extending in the radial direction. This intersection point P2 is a position on the tread surface 22 corresponding to the edge of the second reference layer B2.

In FIG. 6B, the double arrow S1 is measured along the tread surface 22 from the inner edge 56u of the shoulder land portion 26s to the position P1 on the tread surface 22 corresponding to the end of the first reference layer B1. length. In the present invention, this length S1 is the actual width of the first reference layer B1 within the shoulder land portion 26s. The double arrow S2 is the length measured along the tread surface 22 from the inner edge 56u of the shoulder land portion 26s to the position P2 on the tread surface 22 corresponding to the end of the second reference layer B2. In the present invention, this length S2 is the actual width of the second reference layer B2 within the shoulder land portion 26s. A double arrow RS in FIG. 6(b) indicates the actual width of the shoulder land portion 26s shown in FIG.

In this tire 2, the ratio of the actual width S1 of the first reference layer B1 in the shoulder land portion 26s to the actual width RS of the shoulder land portion 26s is preferably 0.8 or more. Thereby, in this tire 2 , the belt 14 sufficiently restrains the tread 4 . In this tire 2, since the peculiar dimensional growth at the outer edge portion of the shoulder land portion 26s is suppressed, the shoulder land portion 26s is prevented from being worn down. In this tire 2, the occurrence of uneven wear is suppressed. From this point of view, this ratio is more preferably 0.85 or more.

In this tire 2, the ratio of the actual width S1 of the first reference layer B1 in the shoulder land portion 26s to the actual width RS of the shoulder land portion 26s is preferably 1.00 or less. Thereby, in this tire 2, the binding force of the belt 14 to the shoulder land portion 26s is appropriately maintained. Regarding the tire circumference, the difference in circumference between the circumference of the equator portion and the circumference of the edge PE of the tread surface 22 is appropriately maintained, so that the shoulder land portion 26s is prevented from slipping on the road surface. In this tire 2, the occurrence of uneven wear such as uneven wear is suppressed.

In this tire 2, the ratio of the actual width S2 of the second reference layer B2 in the shoulder land portion 26s to the actual width RS of the shoulder land portion 26s is preferably 0.6 or more. Thereby, in this tire 2 , the second reference layer B<b>2 contributes to restraining the tread 4 . In this tire 2, since the belt 14 sufficiently restrains the entire tread 4, peculiar dimensional growth at the outer edge portion of the shoulder land portion 26s is suppressed. In this tire 2, the occurrence of uneven wear such as shoulder drop wear is suppressed. From this point of view, this ratio is more preferably 0.70 or more.

In this tire 2, the ratio of the actual width S2 of the second reference layer B2 in the shoulder land portion 26s to the actual width RS of the shoulder land portion 26s is preferably 0.9 or less. Thereby, in this tire 2, the binding force of the belt 14 to the shoulder land portion 26s is appropriately maintained. Regarding the tire circumference, the difference in circumference between the circumference of the equator portion and the circumference of the edge PE of the tread surface 22 is appropriately maintained, so that the shoulder land portion 26s is prevented from slipping on the road surface. In this tire 2, the occurrence of uneven wear such as uneven wear is suppressed. From this point of view, this ratio is more preferably 0.85 or less.

In FIG. 6(b), a double arrow B indicates the thickness of the tire 2 at the equator PC. This thickness B is measured along the equatorial plane. A double arrow E is the thickness of the tire 2 at the edge PE of the tread surface 22 . This thickness E is measured along the normal to the inner surface of the tire 2 passing through the edge PE of the tread surface 22 .

In this tire 2, the thickness E of the tire 2 at the edge PE of the tread surface 22 is preferably greater than the thickness B of the tire 2 at the equator PC. In this tire 2, the rigidity of the shoulder land portion 26s is sufficiently ensured. Since the shoulder land portion 26s has appropriate rigidity, the shoulder land portion 26s is less likely to be worn. In this tire 2, uneven wear is effectively suppressed. From this point of view, the ratio of the thickness E of the tire 2 at the edge PE of the tread surface 22 to the thickness B of the tire 2 at the equator PC is preferably 1.38 or more and preferably 1.45 or less.

As is clear from the above description, according to the present invention, a heavy-duty pneumatic tire 2 in which the occurrence of uneven wear is suppressed is obtained.

The embodiments disclosed this time are illustrative in all respects and are not restrictive. The technical scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configuration described in the claims.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited only to these Examples.

[Example 1]
A heavy-duty pneumatic tire (tire size=12R22.5) having the basic configuration shown in FIG. 1 and the specifications shown in Table 1 below was obtained.

In Example 1, the ratio of the width RS of the shoulder land portion to the width RC of the center land portion (RS/RC) was 1.4. The ratio of the width GS of the shoulder circumferential groove to the width GC of the center circumferential groove (GS/GC) was 0.85. Center stretch Sc was 2.6%. The shoulder stretch Ss was 2.0%. Therefore, the ratio of center stretch Sc to shoulder stretch Ss was 1.3.

In Example 1, narrow vertical grooves and narrow land portions are provided. This is indicated by a "Y" in the Detail column of Table 1.

In this Example 1, the overall value of RRO at the shoulder portion of the tread was 1.1 mm. This is shown in the "OA" column of the table. The absolute value of the difference between the RRO overall value at the center portion and the RRO overall value at the shoulder portion was 0.3 mm. This is shown in the " OA difference" column of the table. The absolute value (maximum value) of the difference between the RRO at the center portion and the RRO at the shoulder portion at each portion in the circumferential direction of the tread was 0.15 mm. This is shown in the " RRO Difference" column of the table. The RRO was measured using a uniformity tester after the tire was mounted on a rim (8.25×22.5), filled with air, and the internal pressure was adjusted to 850 kPa.

In this Example 1, the inclination angle Ac of the belt cords on the equatorial plane was 50° in the first layer of the belt, that is, the third reference layer. In the second layer of the belt, ie the first reference layer, the inclination angle Bc of the belt cords at the equatorial plane was 15°. In the third layer of the belt, ie the second reference layer, the inclination angle Cc of the belt cords at the equatorial plane was 15°. In the fourth layer of the belt, ie, the fourth reference layer, the belt cord had an inclination angle Dc of 18° on the equatorial plane.

In this Example 1, in the first reference layer, the inclination angle Be at the layer edge of the belt cord was equal to the inclination angle Bc at the equatorial plane. That is, the difference (Be-Bc) between the inclination angle Be and the inclination angle Bc was 0°. This is indicated by "0" in the angular difference column of Table 1.

In this Example 1, the first reference layer was constructed such that the belt cord density βc at the equatorial plane and the belt cord density βe at the layer edge were equal. That is, the difference (βe−βc) between the belt cord density βe at the layer edge and the belt cord density βc at the equator plane was 0 ends/5 cm. This is indicated by a "0" in the density difference column of Table 1.

[Examples 2-5 and Comparative Example 2]
Tires of Examples 2 to 5 and Comparative Example 2 were obtained in the same manner as in Example 1 except that the ratio (Sc/Ss), center stretch Sc and shoulder stretch Ss were as shown in Table 1 below. In the tires of Example 2-5 and Comparative Example 2, the angle difference, the density difference, the overall value of RRO in the shoulder portion, the absolute value (maximum value) of the difference between the RRO in the center portion and the RRO in the shoulder portion, and the center portion Table 1 shows the absolute value of the difference between the RRO overall value at the shoulder portion and the RRO overall value at the shoulder portion.

[Example 6 and Comparative Example 1]
The ratio (RS/RC), the ratio (GS/GC), the ratio (Sc/Ss), the center stretch Sc and the shoulder stretch Ss were adjusted as shown in Table 1 below without providing narrow longitudinal grooves and narrow land portions. Tires of Example 6 and Comparative Example 1 were obtained in the same manner as in Example 1 except for the above. In the tires of Example 6 and Comparative Example 1, the angle difference, the density difference, the overall value of RRO in the shoulder portion, the absolute value (maximum value) of the difference between the RRO in the center portion and the RRO in the shoulder portion, and the RRO in the center portion Table 1 shows the absolute value of the difference between the overall value of RRO and the overall value of RRO in the shoulder portion. It should be noted that "N" in the column of thin land portions in Table 1 indicates that neither the thin vertical grooves nor the thin land portions are provided in Example 6 and Comparative Example 1.

[Uneven wear]
The prototype tire was mounted on a rim (size=8.25×22.5) and filled with air to adjust the internal pressure of the tire to 850 kPa. This tire was attached to the front axle of an express bus, and the express bus was run for six months without rotating the tires. After running, the appearance of the tire was observed to confirm the occurrence of uneven wear. The results are shown in Table 1 below with the following ratings.
A: When the occurrence of uneven wear is suppressed B: When uneven wear occurs but no change in running performance is observed C: Uneven wear occurs and there is no problem with running When a degree of deterioration in performance is observed D: When it is determined that uneven wear has occurred and replacement is necessary

As shown in Table 1, it is confirmed that the occurrence of uneven wear is suppressed in the examples. Examples are evaluated higher than Comparative Examples. From this evaluation result, the superiority of the present invention is clear.

The technique for suppressing the occurrence of uneven wear described above can be applied to various tires.

2 Tire 2r Raw tire 4 Tread 6 Side wall 8 Bead 10 Chafer 12 Carcass 14 Belt 21 Fiber reinforcing layer 22... Outer surface (tread surface)
24, 24c, 24s Circumferential grooves 26, 26c, 26s, 26m Land portion 36 Carcass ply 38 Body portion 40 Folded portion 46, 46A, 46B, 46C, 46D Layer 46c Belt cord 50 Narrow vertical groove 52 Narrow land portion 54c Crown portion 54s Side portion B1 First reference layer B2 Second Reference layer B3... Third reference layer B4... Fourth reference layer M... Mold BD... Bladder

Claims (15)

A heavy-duty pneumatic tire comprising a tread in contact with a road surface and a belt positioned radially inside the tread , wherein the tread is laminated on the belt ; and a vulcanizing device comprising a mold for molding the tire. A method for manufacturing using
preparing a green tire including the tread and the belt;
A step of putting the raw tire into a mold;
A step of expanding the diameter of the green tire in the mold and pressurizing and heating it,
The belt is composed of a plurality of layers laminated in a radial direction, and among the plurality of layers, the layer having the widest axial width is a first reference layer, and is laminated on the outer side of the first reference layer. the layer is a second reference layer, the radially innermost layer is a third reference layer, the third reference layer is positioned inside the first reference layer, and
The ratio of the center stretch Sc represented by the following formula (2) at the center of the third reference layer to the shoulder stretch Ss represented by the following formula (1) at the end of the third reference layer is 1 above 3 or less,
A method for manufacturing a heavy-duty pneumatic tire, wherein the shoulder stretch Ss is 1% or more.
(Shoulder stretch Ss) 100×(Rsa−Rsb)/Rsb (1)
(Center stretch Sc) 100×(Rca−Rcb)/Rcb (2)
(where Rsa is the inner diameter of the edge of the third reference layer in the tire, Rsb is the inner diameter of the edge of the third reference layer of the green tire, and Rca is the inner diameter of the center of the third reference layer of the tire. and Rcb is the inner diameter of the center of the third reference layer in the raw tire.) The method for manufacturing a heavy duty pneumatic tire according to claim 1, wherein the shoulder stretch Ss is 2% or less. The overall radial runout value at the center portion of the tread is 1.5 mm or less,
3. The method for manufacturing a heavy duty pneumatic tire according to claim 1, wherein the overall value of radial runout at the shoulder portion of the tread is 1.5 mm or less. 4. The method for manufacturing a heavy duty pneumatic tire according to claim 3, wherein the absolute value of the difference between the overall value of the radial runout at the center portion and the overall value of the radial runout at the shoulder portion is 0.5 mm or less. 5. The manufacturing of the heavy duty pneumatic tire according to claim 3, wherein the absolute value of the difference between the radial runout at the center portion and the radial runout at the shoulder portion is 0.20 mm or less at each portion in the circumferential direction of the tread. Method. the tread comprises a tread surface having a radially outwardly convex profile;
By forming at least three circumferential grooves in the tread, at least four land portions arranged in parallel in the axial direction are formed. and the land portion located on the outer side in the axial direction is the shoulder land portion,
The method for manufacturing a heavy duty pneumatic tire according to any one of claims 1 to 5, wherein each of the plurality of layers constituting the belt includes a large number of belt cords inclined with respect to the circumferential direction. wherein the at least three circumferential grooves include a center circumferential groove located on the inner side in the axial direction and a shoulder circumferential groove located on the outer side;
The method for manufacturing a heavy duty pneumatic tire according to claim 6, wherein the shoulder circumferential groove is narrower than the center circumferential groove. The method for manufacturing a heavy duty pneumatic tire according to claim 6 or 7, wherein the shoulder land portion extends continuously in the circumferential direction without interruption. the tire includes a narrow land portion located outside the shoulder land portion in the axial direction and extending in the circumferential direction;
A narrow vertical groove is provided between the narrow land portion and the shoulder land portion,
The method for manufacturing a heavy-duty pneumatic tire according to any one of claims 6 to 8, wherein the thin longitudinal grooves are located outside the ends of the first reference layer in the axial direction. The method for manufacturing a heavy duty pneumatic tire according to any one of claims 6 to 9, wherein the actual width of the shoulder land portion is wider than the actual width of the center land portion. The method for manufacturing a heavy duty pneumatic tire according to any one of claims 6 to 10, wherein, in the first reference layer, the inclination angle at the layer edge of the belt cord is equal to the inclination angle at the equatorial plane. 12. The production of the heavy duty pneumatic tire according to any one of claims 6 to 11, wherein in the first reference layer and the second reference layer, the belt cord has an inclination angle of 12° or more and 20° or less with respect to the equatorial plane. Method. The heavy duty pneumatic tire according to any one of claims 6 to 12, wherein the axial width of the first reference layer is equal to or narrower than the axial width of the tread surface. Production method. The tread surface includes a crown portion including the equator of the tire, and a pair of side portions each positioned outside the crown portion in the axial direction,
The profile of the crown portion is represented by an arc having a radius Rc, the profile of the side portion is represented by an arc having the radius Rs,
The method for manufacturing a heavy duty pneumatic tire according to any one of claims 6 to 13, wherein the radius Rs of the arc representing the profile of the side portion is larger than the radius Rc of the arc representing the profile of the crown portion. 15. Any of claims 6 to 14, wherein the tire thickness measured along the normal to the inner surface of the tire passing through the edge of the tread surface is greater than the tire thickness measured along the equatorial plane. A method for manufacturing the heavy-duty pneumatic tire described.

Images